BOWIE-ALIGN: substellar metallicity and carbon depletion in the aligned TrES-4b with <i>JWST</i> NIRSpec transmission spectroscopy

ABSTRACT The formation and migration history of a planet is expected to be imprinted in its atmosphere, in particular its carbon-to-oxygen (C/O) ratio and metallicity. The BOWIE-ALIGN (Bristol, Oxford, Warwick, Imperial, Exeter – A spectral Light Investigation into gas Giant origiNs) programme is performing a comparative study of JWST spectra of four aligned and four misaligned hot Jupiters, with the aim of characterizing their atmospheres and corroborating the link between the observables and the formation history. In this work, we present the $2.8-5.2$ µm transmission spectrum of TrES-4 b, a hot Jupiter with an orbit aligned with the rotation axis of its F-type host star. Using free chemistry atmospheric retrievals, we report a confident detection of H$_2$O at an abundance of $\log X_\mathrm{H_2O}=-2.98^{+0.68}_{-0.73}$ at a significance of $8.4\sigma$. We also find evidence for CO and small amounts of CO$_2$, retrieving abundances $\log X_\mathrm{CO}= -3.76^{+0.89}_{-1.01}$ and $\log X_\mathrm{CO_2}= -6.86^{+0.62}_{-0.65}$ ($3.1\sigma$ and $4.0\sigma$, respectively). The observations are consistent with the atmosphere being in chemical equilibrium; our retrievals yield $\mathrm{C/O}$ between $0.30-0.42$ and constrain the atmospheric metallicity to the range $0.4-0.7\times$ solar. The inferred substellar properties (C/O and metallicity) challenge traditional models, and could have arisen from an oxygen-rich gas accretion scenario, or a combination of low-metallicity gas and carbon-poor solid accretion.

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Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-04-01
DOI
https://doi.org/10.1093/mnras/staf530
Citations
6
Primary Topic
High-pressure geophysics and materials
Type
article
Field-Weighted Citation Impact
11.20

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article

BOWIE-ALIGN: substellar metallicity and carbon depletion in the aligned TrES-4b with JWST NIRSpec transmission spectroscopy

Mercedes López‐Morales, Eva-Maria Ahrer, Duncan Christie, Annabella Meech et al.
6 citations
Monthly Notices of the Royal Astronomical Society
High-pressure geophysics and materials
11.20
article

BOWIE-ALIGN: substellar metallicity and carbon depletion in the aligned TrES-4b with JWST NIRSpec transmission spectroscopy

Mercedes López‐Morales, Eva-Maria Ahrer, Duncan Christie, Annabella Meech, James E. Owen, Mason McCormack, Jake Taylor, Maria Zamyatina, Richard A Booth, P. J. Wheatley, James Kirk, Anna B. T. Penzlin, Diana Powell, Daniel T. Valentine, Nathan J. Mayne, Lili Alderson, Vatsal Panwar, Denis E. Sergeev, Hannah R. Wakeford, E. Esparza-Borges, Alastair B Claringbold, Charlotte Fairman
article en
6 citations

Abstract

ABSTRACT The formation and migration history of a planet is expected to be imprinted in its atmosphere, in particular its carbon-to-oxygen (C/O) ratio and metallicity. The BOWIE-ALIGN (Bristol, Oxford, Warwick, Imperial, Exeter – A spectral Light Investigation into gas Giant origiNs) programme is performing a comparative study of JWST spectra of four aligned and four misaligned hot Jupiters, with the aim of characterizing their atmospheres and corroborating the link between the observables and the formation history. In this work, we present the $2.8-5.2$ µm transmission spectrum of TrES-4 b, a hot Jupiter with an orbit aligned with the rotation axis of its F-type host star. Using free chemistry atmospheric retrievals, we report a confident detection of H$_2$O at an abundance of $\log X_\mathrm{H_2O}=-2.98^{+0.68}_{-0.73}$ at a significance of $8.4\sigma$. We also find evidence for CO and small amounts of CO$_2$, retrieving abundances $\log X_\mathrm{CO}= -3.76^{+0.89}_{-1.01}$ and $\log X_\mathrm{CO_2}= -6.86^{+0.62}_{-0.65}$ ($3.1\sigma$ and $4.0\sigma$, respectively). The observations are consistent with the atmosphere being in chemical equilibrium; our retrievals yield $\mathrm{C/O}$ between $0.30-0.42$ and constrain the atmospheric metallicity to the range $0.4-0.7\times$ solar. The inferred substellar properties (C/O and metallicity) challenge traditional models, and could have arisen from an oxygen-rich gas accretion scenario, or a combination of low-metallicity gas and carbon-poor solid accretion.

Monthly Notices of the Royal Astronomical SocietyVol. 539(2)
Space Telescope Science Institute (US), University of Leeds (GB), Universidad de La Laguna (ES), Cornell University (US), University of Exeter (GB), University of Bristol (GB), University of Warwick (GB), University of Oxford (GB), University of Chicago (US), Max Planck Institute for Astronomy (DE), Université Bourgogne Franche-Comté (FR), Center for Astrophysics Harvard & Smithsonian (US), Instituto de Astrofísica de Canarias (ES), Bristol Robotics Laboratory (GB), Imperial College London (GB)
National Aeronautics and Space Administration, Space Telescope Science Institute, Government of the United Kingdom, UK Research and Innovation, Leverhulme Trust, Imperial College London, HORIZON EUROPE Framework Programme, Science and Technology Facilities Council
Openalex Percentile: Top 1%
High-pressure geophysics and materials
11.20
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